Historical:Chalfin Member

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Handbook of Illinois Stratigraphy
Series Bulletin 95
Author H. B. Willman, Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, Jack A. Simon
Date 1975
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Lithostratigraphy: Mammoth Cave Limestone Megagroup >>Salem Limestone >>Chalfin Member
Chronostratigraphy: Paleozoic Erathem >>Mississippian Subsystem >>Valmeyeran Series
Allostratigraphy: Kaskaskia Sequence

Authors

Elwood Atherton, Charles Collinson, and Jerry A. Lineback

Name Origin

The Chalfin Member of the Salem Limestone (Baxter, 1960a, p. 24-27) is named for the village of Chalfin Bridge, Monroe County.

Type Section

The type section of the Chalfin Member is in the Mississippi River bluffs 1 mile southwest of the village of Chalfin Bridge (NE SW 7, 4S-10W), where the member is 39.5 feet thick.

Extent and Thickness

The Chalfin is 26-57 feet thick in the outcrop area.

Description

The Chalfin consists of varying thicknesses of fine-grained limestone; fine- to medium-grained, fossiliferous, locally oolitic limestone; and semilithographic limestone, some of it brecciated. The lower 10 feet is predominantly a calcarenite composed of bryozoan detritus, crinoid columnals, microcrystalline pellets, and a few oolites.

Fossils

Eoendothyranopsis group pressus-rarus, Koninckopora sahariensis, K. inflata, Septabrunsiina, and profuse Calcisphaera characterize the Chalfin.

References

BAXTER, J. W., 1960a, Salem Limestone in southwestern Illinois: Illinois State Geological Survey Circular 284, 32

ISGS Codes

Stratigraphic Code Geo Unit Designation
5200
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